A Commonwealth realm is a sovereign state in which Queen Elizabeth II is the reigning constitutional monarch and head of state. Each realm functions as an independent co-equal kingdom from the other realms. As of 2019, there are 16 Commonwealth realms: Antigua and Barbuda, Australia, The Bahamas, Barbados, Belize, Canada, Grenada, Jamaica, New Zealand, Papua New Guinea, Saint Kitts and Nevis, Saint Lucia, Saint Vincent and the Grenadines, Solomon Islands, Tuvalu, and the United Kingdom. All 16 Commonwealth realms are members of the Commonwealth of Nations, an intergovernmental organisation of 53 member states. Elizabeth II is head of the Commonwealth.

In 1952, Britain's proclamation of Elizabeth II's accession used the term realms to describe the seven sovereign states of which she was queen—the United Kingdom, Canada, Australia, New Zealand, South Africa, Pakistan and Ceylon. Since then, new realms have been created through independence of former colonies and dependencies and some realms have become republics.

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